Discharge of vibrated granular silo: A grain scale approach

The present work focuses on granular flows in a nearly-2D silo when external vibrations are applied. Experimental measurements and numerical simulations based on discrete element method (DEM) were performed in order to study the impact of both vibrations and opening size on the flow. Although vibrations make the flow possible for small opening sizes, we show that they can either increase or decrease the flow rate depending on the range of experimental parameters (amplitude, frequency, opening size...). The effect of vibrations amplitude (10-16000 mu m) and frequency (15-75 Hz) on the flow was investigated. Two regimes are evidenced for the flow, governed by the Froude number Fr and the relative frequency Omega. In the first regime, vibration causes dead zones to flow and increases collision dissipation at the aperture while keeping the particle volume fraction constant. The flow rate decreases and can be described by Benyamine's law by introducing an effective velocity that accounts for the effect of vibrations on the fall of particles at the outlet. In the second regime, the perturbations due to vibrations then surpass the gravity driven flow, leading to periodic shocks in the silo and increasing the apparent flow rate. (C) 2021 Elsevier B.V. All rights reserved.